bi0482452_si_001.pdf (122.9 kB)
Structure of an Oligodeoxynucleotide Containing a Butadiene Oxide-Derived N1 Beta-Hydroxyalkyl Deoxyinosine Adduct in the Human N-ras Codon 61 Sequence†
journal contribution
posted on 2005-03-08, 00:00 authored by Tandace A. Scholdberg, W. Keither Merritt, Stephen M. Dean, Agnieska Kowalcyzk, Constance M. Harris, Thomas M. Harris, Carmelo J. Rizzo, R. Stephen Lloyd, Michael P. StoneThe solution structure of the N1-(1-hydroxy-3-buten-2(S)-yl)-2‘-deoxyinosine adduct arising
from the alkylation of adenine N1 by butadiene epoxide (BDO), followed by deamination to deoxyinosine,
was determined, in the oligodeoxynucleotide d(CGGACXAGAAG)·d(CTTCTCGTCCG). This oligodeoxynucleotide contained the BDO adduct at the second position of codon 61 of the human N-ras protooncogene,
and was named the ras61 S-N1−BDO-(61,2) adduct. 1H NMR revealed a weak C5 H1‘ to X6 H8 NOE,
followed by an intense X6 H8 to X6 H1‘ NOE. Simultaneously, the X6 H8 to X6 H3‘ NOE was weak. The
resonance arising from the T17 imino proton was not observed. 1H NOEs between the butadiene moiety
and the DNA positioned the adduct in the major groove. Structural refinement based upon a total of 364
NOE-derived distance restraints yielded a structure in which the modified deoxyinosine was in the high
syn conformation about the glycosyl bond, and T17, the complementary nucleotide, was stacked into the
helix, but not hydrogen bonded with the adducted inosine. The refined structure provided a plausible
hypothesis as to why this N1 deoxyinosine adduct strongly coded for the incorporation of dCTP during
trans lesion DNA replication, both in Escherichia coli [Rodriguez, D. A., Kowalczyk, A., Ward, J. B. J.,
Harris, C. M., Harris, T. M., and Lloyd, R. S. (2001) Environ. Mol. Mutagen. 38, 292−296], and in
mammalian cells [Kanuri, M., Nechev, L. N., Tamura, P. J., Harris, C. M., Harris, T. M., and Lloyd, R.
S. (2002) Chem. Res. Toxicol. 15, 1572−1580]. Rotation of the N1 deoxyinosine adduct into the high syn
conformation may facilitate incorporation of dCTP via Hoogsteen-type templating with deoxyinosine,
thus generating A-to-G mutations.